The present invention relates generally to organic syntheses of materials to achieve removal of low molecular weight ionic species, such as transition metal ions including cobalt, iron, nickel, and zinc, from aqueous solutions.
Synthesis of polyamine sequestration resin as an intermediate in chemical methodologies for producing polycarboxylic acid chelants is well known. Such chelants are applied to separation processes for removal of both transition metal cations and alkali metal cations from aqueous solution using coordination sequestration as opposed to ion exchange. However, neither synthesis of a nuclear grade resin that would be used for an ion exchange process that none-the-less employs a non-ionic association chemistry to achieve sequestration of the analyte nor the use of these sequestration resins for transition metal cation separations have been done.
The reason to use the polyamine intermediate as opposed to the carboxylic acid based chelant is that the chelants have a capacity that is too strongly pH dependent. In addition, transition metal hydroxide precipitates are known to form within the pores of the carboxylic acid chelants, and finally the geometry of the amine based ligands is more easily tailored specifically to the analyte cation of interest since the carboxylic acid chelants tend to be more highly branched.
Trace amounts of radiocobalts for example are the principle source of personnel radiation dose during refueling outages at light water reactors and at present they are removed from the reactor coolant system mostly during the initial stages of the reactor shutdown procedures thereby causing significant delays in outage critical path. Because no ion exchange cleanup system is efficient enough to cleanup the coolant during operation most of the radiocobalts end up either causing outage dose or outage delays.